Directional control assembly particularly for a winch

Abstract

 A mechanical limit control device for adjustably halting the operation of a winch (102) at preset points including a proportionally driven flexible cog belt (17) providing a compact conformable configuration having projections (27) which operate a snap action air valve (3) to limit the deployment extent of a pneumatically operated winch.

Description

[0001] This invention relates generally to a directional control assembly for a winch and more particularly to a mechanical limit device for adjustably halting the operation of a winch at a preset point in the machine cycle.

[0002] A mechanical limit device can be generally described as a device that halts the operation of a machine at a preset point in the machine's cycle and prevents further operation until the device is reset by some action. A device of this type is often used on a winch to limit the raising and lowering point extent of a load. Once the limit has been reached, the operator would normally be required to reverse the winch for a certain distance in order to reset the device.

[0003] Two common types of mechanical device in current use today are either rotary or linear devices driven through gear reduction by the machine. Rotary devices are geared to track the movement of the machine in less than one revolution of a cam which is used to activate a switch to turn off the machine. Similarly, a linear device is geared to track the movement of the machine by employing a threaded nut travelling along a lead screw to activate a switch. The closer the tracking movement is to the movement of the machine, the greater will be the accuracy of the device and this determines the. exact stopping point at each present limit and the minimum operating distance between the limits. For increased tracking movement, it is desirable to make the cam in a rotary device as large a diameter as possible and the lead screw in a linear device as long as possible. Rotary devices are generally preferred since they will continue to rotate beyond one revolution should the switch fail to stop the machine as intended. If the switch on a linear device should fail to stop the machine, the travelling nut will eventually reach the end of the lead screw. At this point it must disengage to avoid damage to the components. Once disengaged, it will require retiming before it can function again.

[0004] According to the present invention, there is provided
   a directional control assembly characterised by
   a means for producing a first signal of a ratioed position indicating proportionality;
   a means for producing a second signal indicative of an adjustable preset limit of said first signal; and
   said means for producing said first signal including an endless belt.

[0005] For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: -

Figure 1 is a cross sectional view of an air operated winch;

Figure 2 is an external end view of a control unit showing its major component parts;

Figure 3 is an internal cross sectional view of the control unit;

Figure 4 is a cross sectional view of the control unit taken at Section 4-4 of Figure 3 showing a guide pulley relationship;

Figure 5 is an expanded cross sectional view of the directional control valve;

Figure 6 is an expanded cross sectional view showing details of endless belts and coacting poppet valve assembly;

Figure 7 is a partial cross sectional view of the control valve taken at Section 7-7 of Figure 3;

Figure 8 is a cross sectional detail of the poppet valve assembly; and

Figure 9 is an expanded cross sectional detail of the poppet.

[0006] Referring to Figure 1, the limit device and directional control valve assembly 100 are mounted on a winch partially shown and generally indicated by the reference numeral 101 as shown. The rotation of the winch drum 102 is transferred at reduced rate through a spiral gear 103 and drive shaft 13 (best seen in Figure 6) to a worm gear 11 (best seen in Figure 4) in the limit device. Actuation of the directional control valve 105 causes the winch drum 102 to turn and drive belts in the limit device to turn at reduced rate.

[0007] Referring to Figures 1 and 6, the winch drum 102 will continue to turn until a raised. portion 27 on an appropriate dual belt toothed drive belt 17 or 17a in the limit device passes over a support guide 12 and lifts a poppet 3 aligned with that belt. This will cause an air valve to snap close and stop the winch drum. Counterclockwise rotation of the winch drum for approximately one revolution will reset the air valve. Counterclockwise drum rotation will be restricted in the same manner by the opposite belt and air valve in the limit device.

[0008] Referring to Figure 4, the number of drum revolutions in either direction can be adjusted by repositioning the belts. For clockwise (raise) rotation, the winch drum 102 would be rotated to the desired upper limit position, set screws 37 would then be loosened and the left hand adjusting hub 5c turned counterclockwise until the raised portion of the belt lifts the poppet, this is signalled by air release down the poppet stem. The set screws 37 would then be tightened. For counterclockwise rotation, the procedure would be repeated using the right hand adjusting hub 5b and turning it clockwise.

[0009] Referring generally to Figures 3 and 4, the present assembly employs the flexible toothed belts 17 and 17a, which have raised areas 27 which activate snap acting air valves to limit the raising and lowering points on an air driven winch. One belt is used for the upper limit control and one for the lower limit control. The snap acting air valves are incorporated in the limit device housing and these control the air supply to a directional pilot valve that is also mounted on the housing. This arrangement provides an efficient modular control package that minimises external piping and fittings and enables simple installation, service and timing adjustment.

[0010] Like the cam device, the belts provide endless rotation; like the lead screw device, the belts provide part of the overall gear ratio. Since the belts are flexible, the shape of the housing can be tailored to suit the shape of other components on the winch. Also, they can be packaged into a housing less than half the size of the equivalent cam or lead screw. Unlike the cam or lead screw, the belts are free from backlash, impervious to contamination and do not corrode. In a typical installation, the belts will reduce the required gear reduction to one third of that required by a cam device. This also reduces the backlash to one third and thus the minimum operating distance between limits to one third.

[0011] Pressure differential principles create an "over centre" condition in the air valves in this device causing them to consistently snap open or close at the same actuation point. This greatly improves accuracy since, on a winch having a large amount of cable, the tracking movement of the belts is small when compared to the movement cable and even a small variation in the opening or closing point of an air valve can cause the preset limit to vary several feet (1 foot = 0.3048 m).

[0012] Referring to Figures 4 and 6, the toothed flexible timing belts 17 and 17a are mounted on toothed pulleys 5a and 5b and pass over tensioner pulleys 7a and 7b all carried inside the housing 1. The belts 17 and 17a also pass over tensioning support guide 12 which is adjustably secured by screws 25 to housing 1. The belts 17 and 17a each have a .03 inch (0.76 mm) thick rubber strip 27 bonded to the smooth side.

[0013] The right hand pulley assembly comprises the adjustment hub 6, toothed pulley 5a, toothed pulley 5b and worm gear 11. The toothed pulley 5a and worm gear 11 are selectively free to rotate about the adjustment hub 6 while the toothed pulley 5b is permanently bonded to the adjustment hub 6 to prevent any relative movement. When tightened, the lock screws 37 clamp the toothed pulley 5a and worm gear 11 against the toothed pulley 5b and prevent rotation relative to the adjustment hub 6, which is mounted on pin 23 pressed into housing 1 and is free to rotate. The right hand pulley assembly is driven through the worm gear 11 by the worm 16 mounted on the drive shaft 13 carried by bearing 18. Drive shaft 13 is driven through a spiral gear that is connected to the winch drum.

[0014] The left hand pulley assembly comprises the hub 6a, toothed pulley 5c, toothed pulley 5d and spacer 10. The toothed pulley 5d and spacer 10 are free to rotate about the adjustment hub 6a and the toothed pulley 5c is permanently bonded to the hub 6a to prevent any relative movement. The hub 6a is mounted on a pin 23a pressed into the housing 1 and is free to rotate.

[0015] The centre pulley assembly is used to adjust belt tension and also serves to maximise the belt length and comprises flanged pulleys 7a and 7b and spacer 9 free to rotate on the shaft 8 but axially retained by retaining ring 29. The shaft 8 is eccentrically secured to the housing 1 by a screw 25 which when slackened, allows the shaft 8 to pivot about the screw 25 in an arc sufficient to slacken or tighten the belt.

[0016] Referring to Figures 3, 6, 8 and 9, the snap acting valve assembly comprises the poppet assembly 3, sleeve 22 and poppet seat 4. The poppet assembly 3 comprises poppet 1, upper rubber face seal 2 and lower rubber face seal 2a. The poppet 1 has a crossed drilled hole 31 and a small diameter communicating orifice 32. Sleeve 22 is pressed into housing 1 and slidably locates poppet assembly 3 while also providing a sealing seat for lower face seal 2a. Poppet seat 4 is pressed into the housing 1 so that it provides a sealing seat 33 a small distance above upper rubber face seal 2 on the poppet assembly 3.

[0017] There are two identical snap acting valve assemblies right hand 3 and left hand 3a as described above located in the housing 1 and staggered so that the rounded end of each poppet is positioned above the centre of each belt. The poppet seat 4 has a centre hole of sufficient diameter to provide full flow of air through it. Lower face seal 2a is smaller in diameter than the upper face seal 2. Air under pressure enters the housing 1 and is directed to the right hand and the left valve assemblies creating a pressurised chamber in which each poppet assembly 3 sits.

[0018] This pressure normally forces each poppet assembly downward towards the belts causing each lower face seal 2a to seal on their respective sleeve 22 seats thus preventing air leakage past the stems of the poppets 1. When air is flowing through the poppet seat 4, a small force applied to the rounded end of the poppet causes the poppet to move away from the lower seat and approach the upper seat 4. This action initially reduces the downward force on the poppet since air pressure is now acting only on the stem area and not the lower seat area which is larger.

[0019] As the poppet approaches the upper seat 4, it begins to restrict air flow through it causing a pressure drop above the poppet. The large difference between the area of poppet seat 4 and the area of the poppet stem causes this small pressure drop to suddenly unbalance the poppet forcing it against seat 4. This action cuts off to one side of the directional control valve 30 all but a small supply of air which passes through the small diameter orifice 32 in the poppet 1, through the poppet seat 4, past open check ball 16 and through a bleed hole 36 positioned above in the valve 30. If the check ball 16 closes, this air is trapped causing pressure to build above and the poppet to snap back on to the lower seat.

[0020] Referring to Figures 2 and 5, the directional control valves 30 and 30a provide pressure regulated pilot air to control the amount and direction of spool movement on the winch motor control valve. The regulator assembly comprises the rubber check ball 16 which is guided by the sleeve 8 and held against a seat in the valve body 1 by a spring 14. Also piston 26 which is held in equilibrium by spring 13 acting against valve body 1 and spring 12 acting against plunger 47, which is flange retained by bearing 21 pressed into the valve body. The valve 30 comprises two identical assemblies as just described. The actuator 3 is rotated on pin 48 in the valve body 1 by handle 105 and normally rests loosely on right and left hand plungers 47 and 47a. Slightly rotating actuator 3 clockwise depresses right hand plunger 47 by a small amount which moves the piston 6 downward by compressing high rate spring 12 against low rate spring 13 causing it to bottom out. The piston 6 has a tapered nose which contacts rubber check ball 16 sealing a small diameter bleed hole 36 at the centre of the piston 6 as the check ball is lifted. This permits air to flow into valve chamber 40 and out through channel 41 to one of the pilot chambers on the winch control valve. Pressure builds in the chamber 40 and overcomes the spring 12 by acting on the piston 6 causing it to move back and partially close the check ball 16. In this position a condition of equilibrium exists where the check ball will remain slightly open to maintain pressure and flow. Increasing the clockwise rotation of actuator 3 causes increased compression of spring 12 and thus raises the pressure in the chamber 41. Decreasing the clockwise rotation of actuator 3 will reduce compression on spring 12 causing air pressure in chamber 41 to push the piston 6 back momentarily away from the check.ball 16 allowing air to escape down the centre hole in the piston 6 until the pressure stabilises at a lower value to match the reduced compression on the spring 12. Rotation of the actuator 3 counterclockwise beyond its normal centre position will produce exactly the same results in the opposite pilot channel of the winch control valve.

Claims

1. A directional control assembly (100) characterised by
   a means for producing a first signal of a ratioed position indicating proportionality;
   a means for producing a second signal indicative of an adjustable preset limit of said first signal; and
   said means for producing said first signal including an endless belt (17).

2. An assembly according to claim 1, wherein said means for producing said second signal further comprises a discontinuity (27) of said endless belt.

3. An assembly according to claim 2, wherein said discontinuity (27) includes means for activating a control valve (3).

4. An assembly according to claim 2 or 3, wherein said discontinuity comprises a raised portion (27) on the exterior of said endless belt.

5. An assembly according to claim 3 or 4, wherein said control valve is a snap action poppet valve (3).

6. An assembly according to any one of the preceding claims, wherein said endless belt is a toothed belt.

7. An assembly according to claim 6, wherein a cog wheel (5) is adjustable in rotary position relative to said shaft (23) on which it is mounted.

8. An assembly according to claim 7, wherein said shaft (23) is driven by a gear drive in proportion to the rotation of a winch drum (102) for which the assembly is provided.

9. An assembly according to any one of the preceding claims, wherein said endless belt is tensioned by an idler pulley (7).

10. An assembly according to any one of the preceding claims, wherein said endless belt is adjustable in its ratioed position relative to its position indicating proportionality.

11. A winch drum (102) incorporating a directional assembly for the drum, the assembly being according to any one of the preceding claims.

12. A winch drum according to claim 10, wherein said endless belt provides said first signal which indicates proportionality of the rotary position of winch drum.

Drawing